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Highpoint HPT370 ATA/100
RAID Controller Chip
Last updated: 7/27/00
 This
144-pin chip is starting to show-up on motherboards and ATA/100 controller
expansion boards. What it does is what the motherboard chipsets don't
do yet. It brings ATA/100 performance and a couple of extra
IDE interfaces to motherboards, and RAID features
to IDE hard disk drives. So,
I thought this little gem deserved its own little article...
What is ATA/100? Ultra
ATA/100 is an updated version of the ATA/66 disk drive data bus introduced
by Quantum in 1998. The ATA/100 specification defines a physical
layer operating at 100 megabytes per second (MBs). It is backward
compatible with ATA/33 and ATA/66 enabled devices; i.e., ATA/33 and ATA/66
drives can be connected to an ATA/100 interface. ATA/100 drives
use the same 80-conductor, 40-pin cable introduced for by ATA/66
standard. If an older, 40-pin IDE cable is connected to
an ATA/100 (or ATA/66) interface, it will work; however, the drive will
be treated as an ATA/33 drive or, if older, whatever the drive actually
is.
What is RAID? A RAID or Redundant
Array of Inexpensive Disks is a collection of disk drives that collectively
act as a single storage system. In other words, two or more hard disk drives
which are grouped together and appear as a single disk drive. Or,
in practice, it can also be two or more disk partitions grouped together
and appear as a single partition/logical drive. A partition or volume
is just that, a demarcated and contiguous section of a drive which appears
like a drive--a logical drive. There are six levels of RAID and the
features of more than one level can combined in a RAID. The HPT370
supports three flavors of RAID:
-
Stripping
(RAID Level 0). Provides performance (not redundant
as implied in the acronym). Data is evenly spread over identical
drives. That is, parts of file can be spread over more than
one drive. Data can be read and written in parallel. Performance
is very good. Failure of any one disk in the array results
in data loss. This kind of RAID would be good for storing large
files of temporary nature, but you sure wouldn't want to put you
accounting package on one.
-
Mirroring
(RAID level 1). Provides
redundancy. Two drives duplicate each other identically. If
one drive fails, all of the data is available on the other one. The
read performance of mirrored drives can be increased through load
balancing and elevator sorting (I won't go into elevator sorting
here). Simply
put, when data is requested it is read from the least busy drive. Put
that accounting package on this one; I did. But remember
it is possible for Windows to "scribble" on a hard disk. In
this arrangement, a scribble on one drive is more than likely a "scribble" on
both drives--mirrored garbage is garbage.
-
Striping/Mirroring
(RAID 0+1). Provides performance and redundancy. Two
sets of stripped drives (four drives in the case of the HP370)
are mirrored. This arrangement may be fast and redundant, but
it is also expensive and complicated.
RAID
can be done with software as well as hardware. The configuration
of our Windows NT file server is similar to RAID 1. A critical
partition on the primary drive is mirrored to a like partition on the
secondary drive. We also did it quite a few years ago with two 340
MByte IDE hard disks and another IDE controller in a Novell file server
with a 386 motherboard. SCSI drives have been used in mirrored
configurations for many years. Putting the IDE RAID function/chip
on the motherboard is new.
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